{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T09:34:57Z","timestamp":1773394497982,"version":"3.50.1"},"reference-count":19,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2025,10,1]],"date-time":"2025-10-01T00:00:00Z","timestamp":1759276800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Science and Technology Major Special Project Fund of Changsha","award":["kh2401010"],"award-info":[{"award-number":["kh2401010"]}]},{"DOI":"10.13039\/501100004735","name":"Hunan Provincial Natural Science Foundation","doi-asserted-by":"crossref","award":["2025JJ90177"],"award-info":[{"award-number":["2025JJ90177"]}],"id":[{"id":"10.13039\/501100004735","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100004735","name":"Hunan Provincial Natural Science Foundation","doi-asserted-by":"crossref","award":["2024JJ9173"],"award-info":[{"award-number":["2024JJ9173"]}],"id":[{"id":"10.13039\/501100004735","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Future Internet"],"abstract":"<jats:p>With the widespread adoption of space\u2013air\u2013ground integrated networks (SAGINs) in next-generation wireless communications, intelligent reflecting surfaces (IRSs) have emerged as a key technology for enhancing system performance through passive link reinforcement. This paper addresses the prevalent issue of channel state information (CSI) uncertainty in practical systems by constructing an IRS-assisted multi-hop SAGIN communication model. To capture the performance degradation caused by channel estimation errors, a norm-bounded uncertainty model is introduced. A simulated annealing (SA)-based phase optimization algorithm is proposed to enhance system robustness and improve worst-case communication quality. Simulation results demonstrate that the proposed method significantly outperforms traditional multiple access strategies (SDMA and NOMA) under various user densities and perturbation levels, highlighting its stability and scalability in complex environments.<\/jats:p>","DOI":"10.3390\/fi17100452","type":"journal-article","created":{"date-parts":[[2025,10,1]],"date-time":"2025-10-01T09:37:21Z","timestamp":1759311441000},"page":"452","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Robust Optimization for IRS-Assisted SAGIN Under Channel Uncertainty"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-4711-7278","authenticated-orcid":false,"given":"Xu","family":"Zhu","sequence":"first","affiliation":[{"name":"School of Computer Science, Central South University, Changsha 410083, China"},{"name":"School of Information Engineering, Hunan Industry Polytechnic, Changsha 410208, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Litian","family":"Kang","sequence":"additional","affiliation":[{"name":"School of Computer Science, Central South University, Changsha 410083, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2317-5359","authenticated-orcid":false,"given":"Ming","family":"Zhao","sequence":"additional","affiliation":[{"name":"School of Computer Science, Central South University, Changsha 410083, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"8627","DOI":"10.1109\/TCOMM.2021.3116151","article-title":"RIS-Aided Wireless Communications: Prototyping, Adaptive Beamforming, and Indoor\/Outdoor Field Trials","volume":"69","author":"Pei","year":"2021","journal-title":"IEEE Trans. Commun."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"5720","DOI":"10.1109\/TCOMM.2024.3382332","article-title":"Reconfigurable Intelligent Surface: Power Consumption Modeling and Practical Measurement Validation","volume":"72","author":"Wang","year":"2024","journal-title":"IEEE Trans. Commun."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"110729","DOI":"10.1016\/j.comnet.2024.110729","article-title":"Minimize BER without CSI for dynamic RIS-assisted wireless broadcast communication systems","volume":"253","author":"Gong","year":"2024","journal-title":"Comput. Netw."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Abrardo, A. (2024). CSI-Free Optimization of Reconfigurable Intelligent Surfaces with Interference by Using Multiport Network Theory. arXiv.","DOI":"10.23919\/EuCAP60739.2024.10501476"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"111650","DOI":"10.1016\/j.comnet.2025.111650","article-title":"Joint operating mode and resource allocation optimization in wireless-powered RIS-assisted multiuser communication systems","volume":"272","author":"Yuan","year":"2025","journal-title":"Comput. Netw."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"8238","DOI":"10.1109\/TVT.2019.2923997","article-title":"Large Intelligent Surface-Assisted Wireless Communication Exploiting Statistical CSI","volume":"68","author":"Han","year":"2019","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1911","DOI":"10.1109\/COMST.2024.3421523","article-title":"A survey on resource management in joint communication and computing-embedded SAGIN","volume":"27","author":"Chen","year":"2024","journal-title":"IEEE Commun. Surv. Tutorials"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"90","DOI":"10.23919\/JCC.2022.02.008","article-title":"Space-air-ground integrated network (SAGIN) for 6G: Requirements, architecture and challenges","volume":"19","author":"Cui","year":"2022","journal-title":"China Commun."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Li, X., Li, Y., Song, X., Li, J., and Zhao, S. (2025). Physical Layer Security Analysis of Hybrid FSO\/RF Systems in SAGIN With Channel Imperfection and Interference. IEEE Trans. Aerosp. Electron. Syst., early access.","DOI":"10.1109\/TAES.2025.3576315"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"940","DOI":"10.1109\/TWC.2024.3503060","article-title":"Outage Probability, Performance, and Fairness Analysis of Space\u2013Air\u2013Ground Integrated Network (SAGIN): UAV Altitude and Position Angle","volume":"24","author":"Tan","year":"2025","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"100","DOI":"10.1109\/TCC.2023.3339394","article-title":"Integrated Computation Offloading, UAV Trajectory Control, Edge-Cloud and Radio Resource Allocation in SAGIN","volume":"12","author":"Nguyen","year":"2024","journal-title":"IEEE Trans. Cloud Comput."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"682","DOI":"10.1109\/JIOT.2022.3203895","article-title":"OTFS-aided RIS-assisted SAGIN systems outperform their OFDM counterparts in doubly selective high-Doppler scenarios","volume":"10","author":"Xu","year":"2022","journal-title":"IEEE Internet Things J."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Lin, S., An, J., Gan, L., and Debbah, M. (2025, January 6\u201311). UAV-mounted SIM: A hybrid optical-electronic neural network for DoA estimation. Proceedings of the ICASSP 2025-2025 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Hyderabad, India.","DOI":"10.1109\/ICASSP49660.2025.10890179"},{"key":"ref_14","unstructured":"Fan, M., Sun, G., Pan, H., Wang, J., An, J., Du, H., and Yuen, C. (2025). Joint Association and Phase Shifts Design for UAV-mounted Stacked Intelligent Metasurfaces-assisted Communications. arXiv."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"3057","DOI":"10.1109\/JSAC.2022.3196119","article-title":"Intelligent Reflecting Surface-Aided LEO Satellite Communication: Cooperative Passive Beamforming and Distributed Channel Estimation","volume":"40","author":"Zheng","year":"2022","journal-title":"IEEE J. Sel. Areas Commun."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"3025","DOI":"10.1109\/TVT.2023.3324970","article-title":"Joint optimization design of RIS-assisted hybrid FSO SAGINs using deep reinforcement learning","volume":"73","author":"Wu","year":"2023","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"265","DOI":"10.1016\/j.cja.2021.10.038","article-title":"Robust trajectory planning for UAV communication systems in the presence of jammers","volume":"35","author":"ZHOU","year":"2022","journal-title":"Chin. J. Aeronaut."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"7481","DOI":"10.1109\/JIOT.2021.3108875","article-title":"A GA-based sustainable and secure green data communication method using IoT-enabled WSN in healthcare","volume":"9","author":"Singh","year":"2021","journal-title":"IEEE Internet Things J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1016\/j.comcom.2023.12.025","article-title":"Mobile-IRS assisted next generation UAV communication networks","volume":"215","author":"Shakhatreh","year":"2024","journal-title":"Comput. Commun."}],"container-title":["Future Internet"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-5903\/17\/10\/452\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T08:36:34Z","timestamp":1773390994000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-5903\/17\/10\/452"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,10,1]]},"references-count":19,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2025,10]]}},"alternative-id":["fi17100452"],"URL":"https:\/\/doi.org\/10.3390\/fi17100452","relation":{},"ISSN":["1999-5903"],"issn-type":[{"value":"1999-5903","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,10,1]]}}}